What is the thin layer of air around the Earth called?

• Atmosphere

• Stratosphere

• Troposphere

• Biosphere

What is relative humidity a measure of?

• Moisture content

• Temperature

• Wind speed

• Air pressure

What process do green plants use to make their food?

• Fermentation

• Respiration

• Photosynthesis

• Transpiration

What is the main gas that plants produce during photosynthesis?

• Carbon dioxide

• Oxygen

• Hydrogen

• Nitrogen

What is the ratio of nitrogen to oxygen in the air?

• 4:1

• 5:1

• 2:1

• 1:1

Which gas is most soluble in water?

• Oxygen

• Nitrogen

• Argon

• Carbon dioxide

What is the primary source of carbon dioxide in the air?

• Volcanic eruptions

• Combustion of fuels

• Respiration

• Photosynthesis

What do living organisms in water use to obtain oxygen?

• Photosynthesis

• Air bubbles

• Soil air

• Dissolved oxygen

What is the process called when water vapor condenses into droplets?

• Transpiration

• Precipitation

• Condensation

• Evaporation

What is the main component of air by volume?

• Nitrogen

• Carbon dioxide

• Argon

• Oxygen